As you play through the Octo Canyon single player mode, you'll unlock new Hero Weapons to use as you progress.

Unlockable	How to unlock
Hero Blaster	Unlocked in Lair 19.
Hero Brella	Unlocked in Lair 20.
Hero Brush	Unlocked in Lair 22.
Hero Charger	Unlocked in Lair 06.
Hero Dualies	Unlocked in Lair 05.
Hero Roller	Unlocked in Lair 04.
Hero Shot	Unlocked in Lair 01.
Hero Slosher	Unlocked in Lair 10.
Hero Splatling	Unlocked in Lair 13.